1. Field of the Invention
The present invention relates to an image reader and a document conveying method, and more particularly, to an improvement of an image reader that can, during continuous reading of two or more documents, cancel the reading.
2. Description of the Related Art
An image reader that can automatically convey two or more documents to sequentially read the documents is known. Further, an image reader that can perform double-sided reading of a document through automatic conveyance is also widely known. As an image reader that can perform the double-sided reading, one based on a one-pass two-scanner method that uses two image sensors to perform the double-sided reading of a document, or one based on a two-pass one-scanner method that reverses a document during automatic conveyance, and uses one image sensor to perform the double-sided reading of the document are known.
To perform the double-sided reading based on the two-pass one-scanner method, a switchback system that performs switchback that switches a conveying direction during conveyance of a document, and thereby passes the document twice in the same direction with respect to an image sensor, or a U-turn system that uses a U-turn path to make a conveyance path intersect with itself, and passes a document twice in opposite directions with respect to an image sensor are possible. In the case of using the U-turn system, it is not necessary to switch a conveying direction, so that conveyance control can be simplified, and also a reading time can be shortened (e.g., JPA-2009-10861).
In an image reader that performs such automatic conveyance, typically, during continuous reading of two or more documents, the reading process can be cancelled. For example, in the case where after a start key has been operated, a setting error of the image reader or a mix-up of documents is discovered, a user can operate a stop key to thereby cancel document reading that is being performed. In the case where such a cancel instruction is inputted, without performing the document reading, a discharge process that discharges to a paper discharge tray a document being conveyed is performed. By performing such a discharge process, even in the case of canceling a reading process, the user is not required to take the document out of a conveyance path.
Further, there is also an image reader that, in the case where the cancel instruction is inputted, performs an idle feeding process that sequentially discharges documents left on a paper feed tray to a paper discharge tray. By performing such an idle feeding process, even in the case of canceling a reading process, all documents can be brought into a state of being discharged to the paper discharge tray in the same order as that before reading. For this reason, after canceling the reading, it is not necessary for a user to overlap the documents on the paper feed tray and those on the paper discharge tray while checking the orders of the documents.
In the image reader based on the two-pass one-scanner method, the switchback or U-turn of a document is performed at the time of double-sided reading, so that as compared with single-sided reading, a conveyance length of the document is increased, and a document interval is also increased. For this reason, there occurs a problem that, in the case of canceling the double-sided reading, times necessary for subsequent discharge and idle feeding processes are increased as compared with the case of canceling the single-sided reading.
For example, the image reader based on the U-turn system is typically configured to branch a conveyance path into a single-sided path and a double-sided path, and uses the U-turn path to make only the double-sided path intersect with itself. Accordingly, the double-sided path is longer than the single-sided path, and further at the time of double-sided reading, it is necessary to make a document interval longer than that for the single-sided reading so as to prevent documents from colliding with each other. For this reason, there occurs a problem that, in the case of canceling the double-sided reading, the times necessary for the discharge and idle feeding processes are increased as compared with the case of canceling the single-sided reading.